**Core Concept**
The triangle of auscultation is an anatomical region on the back where sounds from the lungs can be more clearly heard during a physical examination. It is bounded by three muscles: trapezius, latissimus dorsi, and rhomboid major. Understanding the anatomy of this region is crucial for accurate auscultation.

**Why the Correct Answer is Right**
The rhomboid major muscle does not form one of the boundaries of the triangle of auscultation. Instead, it is located more laterally and is involved in the movement of the scapula. The correct boundaries of the triangle of auscultation are formed by the trapezius muscle superiorly, the latissimus dorsi muscle inferiorly, and the scapula medially.

**Why Each Wrong Option is Incorrect**
**Option A:** The trapezius muscle is indeed one of the boundaries of the triangle of auscultation, and it is the superior boundary.
**Option B:** The latissimus dorsi muscle is another correct boundary of the triangle of auscultation, forming the inferior edge.
**Option C:** The scapula is also a correct boundary of the triangle of auscultation, forming the medial edge.

**Clinical Pearl / High-Yield Fact**
The triangle of auscultation is a narrow region on the back where sounds from the lungs can be more clearly heard due to the minimal thickness of the overlying muscles and the proximity of the scapula.

**✓ Correct Answer: D. Rhomboid major**